Impact absorption structure of vehicle seat

ABSTRACT

Impact absorption structure is provided in side frame element of seat cushion frame, wherein the side frame element has a vertical planar portion, an upper flange portion and a lower flange portion. A centroidal line is utilized as important factor, which extends along a vertical section of those vertical planar portion and upper and lower flange portions. Namely, an upper portion of the centroidal line is inclined by a certain angle toward a side inwardly of the seat cushion frame, and a module of section of said lower flange portion is smaller than a module of section of said upper flange portion, thereby allowing the side frame element to be deformed by impact load toward a side outwardly of the seat cushion frame and thus absorbing the impact load. For example, an inward extension may be merely formed in the upper flange portion to realize such impact absorption structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an impact absorption structure of vehicle seat which is so designed that a local part of seat frame is deformable to absorb an impact caused by a great load applied to the seat in the case of a rear-end collision, or in the case of a backward collision wherein, when a vehicle runs backwardly, a backward side of vehicle collides with something hard or other vehicle.

2. Description of Prior Art

When a rear-end collision or a backward collision defined above occurs to a vehicle, a great load is applied from a seat occupant to a seat in the vehicle in a backward direction, thus creating a corresponding great impact to a whole of the seat. That is, a great impact is transmitted backwardly to a seat back of the seat through an upper body portion of an occupant sitting on the seat and imparted to the seat.

Normally, the vehicle seat itself is formed by robust seat frames sufficient to withstand such impact load, for which reason, the load or impact is transmitted straight through the seat frames and intensively exerted upon a relatively vulnerable portion of mechanical part provided in the seat frames, such as a mechanical part of reclining device and/or other peripheral seat adjustment devices. In that case, it is highly possible that the mechanical parts of such seat adjustment devices will be damaged or broken.

In order to solve the forgoing problem, a deformable area is defined in a particular point in the seat frame to effectively absorb the impact load and prevent an extensive exertion of the impact load on the mechanical parts of seat adjustment devices including the reclining device.

One example of such shock absorption arrangement is found from the Japanese Laid-Open Patent Publication No. 7-132767, which teaches a vehicle seat structure wherein a side frame section of the seat back thereof is provided with a deformable area at a predetermined point therein, so that the deformable area will be deformed by an impact load applied to the seat back, to thereby absorb most of the impact load.

However, in this shock absorption structure of seat-back side frame sections, it is difficult to adjust and define the deformable area in an optimum size for each different seat back, and further, there is no disclosure for provision of means for limiting backward inclination of the seat back in the case of the deformable area being deformed to allow such backward inclination. Hence, it is more likely than not that the seat back will be subjected to excessive backward inclination in a collision case.

On the other hand, as disclosed by the Japanese Laid-Open Patent Publication No. 2002-12072, the foregoing locally deformable arrangement is provided in a side frame section of seat cushion frame to effectively absorb the impact load. According to this prior art, the side frame section is connected with a seat slide device and a sector-like deformable area is defined in an accordion fashion in the upper flange portion of the side frame section. With this arrangement, in a backward collision case, the connection point between the side frame section and the seat slide device serves to limit excessive deformation of the seat cushion side frame section as well as excessive backward inclination of the seat back, and also, the sector-like deformable area is deformed to absorb the impact load.

But, such shock absorption structure is defective in that the thus-processed flange portion of the side frame section does not serve its reinforcing and protection functions. That is, the deformable region given in the upper flange portion of side frame section is found defective in decreasing its reinforcement for the upper side of the side frame section itself and does not protect the adjacent trim cover and padding of seat cushion.

In order to solve such problem, it has been a common practice to provide a side frame section of increased thickness to achieve both reinforcement and protection effects, which however results in increase of weight of a whole seat cushion frame. This in turn raises costs for assembly of seat.

SUMMARY OF THE INVENTION

In view of the above-stated drawbacks, it is a purpose of the present invention to provide an improved impact absorption structure of vehicle seat which is simplified in structure and directly applicable to a side frame member of seat cushion frame which has upper and lower flange portions.

In order to achieve such purpose, the impact absorption structure of vehicle seat in accordance with the present invention is basically comprised of:

-   -   a seat cushion frame including a side frame means;     -   the side frame means having a vertical planar portion and a         peripheral flange element formed in the peripheral ends of the         vertical planar potion, wherein the vertical planar portion         includes an upper end facing to a side upwardly of the vehicle         seat and a lower end facing to a side downwardly of the vehicle         seat, and the peripheral flange element includes: an upper         flange portion formed in the upper end of vertical planar         portion; and a lower flange portion formed in the lower end of         vertical planar portion;         -   and     -   a means for making the side frame means prone to deformation by         an impact load to be imparted to the seat cushion frame, the         means including a centroidal line which extends vertically along         a whole vertical section of the side frame means which includes         a vertical section of the upper and lower flange portions, the         centroidal line having an upper portion facing to the side         upwardly of the vehicle seat,     -   wherein the afore-said means is arranged in the whole vertical         section of the side frame means as well as in the vertical         section of the upper and lower flange portions, such that the         upper portion of the centroidal line is inclined by a         predetermined angle in a direction to a side inwardly of the         seat cushion frame, and that a module of section of the lower         flange portion is smaller than a module of section of the upper         flange portion, thereby allowing the side frame means to be         deformed by the impact load toward a side outwardly of the seat         cushion frame, and thus absorbing the impact load.

Preferably, the aforementioned means is arranged in a predetermined local area of the side frame means.

As one aspect of the present invention, with the vertical planar portion of side frame means extending along a plumb line, the foregoing means may comprise an inward extension which is formed in the upper flange portion so as to extend therefrom to a side inwardly of the seat cushion frame, whereby the upper portion of the centroidal line is inclined by the predetermined angle in a direction to the side inwardly of the seat cushion frame, while the module of section of the lower flange portion is smaller than the module of section of the upper flange portion. In this mode, preferably, such inward extension may be formed in and along the upper flange portion at a limited length, so as to allow a local area of the side frame means to be deformed by the impact load in a direction to the side outwardly of the seat cushion frame.

Other various features and advantages of the invention will become apparent from reading of the description, hereinafter, with reference to the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly broken schematic perspective view of a vehicle seat framework to which an impact absorption structure of the present invention is applied;

FIG. 2 is a vertical sectional view of a side frame member of a seat cushion frame to which the impact absorption structure of the present invention is applied;

FIG. 3 is a vertical section view showing a state where a local area of the side frame member is deformed outwardly in the impact absorption structure;

FIG. 4 is a partly broken side view of the seat framework which indicates a relatively large deformable area in the side frame member as one aspect of the impact absorption structure;

and

FIG. 5 is a partly broken side view of the seat framework which indicates a limited small deformable area in the side frame member as another aspect of the impact absorption structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

Referring to FIGS. 1 to 5, there is illustrated a preferred embodiment of impact absorption structure of vehicle seat, as generally designated by (10), in accordance with the present invention.

FIG. 1 shows, in perspective, a seat framework (SF) used in this particular embodiment, which is intended for better understanding of the present invention, but it has to be upheld to form a vehicle seat. Hence, it is to be understood that the seat framework (SF) corresponds to a vehicle seat to which the present invention is applied. The seat framework (SF) typically comprises: a seat back frame (BF) corresponding to a seat back of the vehicle seat; and a seat cushion frame (CF) corresponding to a seat cushion of the vehicle seat, with a known reclining device (RD) operatively provided between those two frames (BF) (CF) for allowing for adjustable inclination of the seat back. Designation (25) denotes a connecting rod operatively connected between two mechanical elements of the reclining device (RD) as known in the art.

The seat back frame (BF) includes a pair of side frame sections (12) (12) and a lower frame section (27). Designation (28) denotes a plurality of sinuous springs extended between the two side frame sections (26), which act as a resilient support for a back of a seat occupant (not shown).

It is noted that the term, “forward” or “forwardly”, refers to a forward side (F) of the seat framework (SF) or vehicle seat, and the term, “backward” or “backwardly”, refers to a backward side (R) of the seat framework (SF) or vehicle seat.

The seat cushion frame (CF) is depicted in FIG. 1 as basically comprising: a pair of side frame members (12) (12); a forward frame member (16); and backward frame member (18). Designation (20) denotes a plurality of sinuous springs extended between the forward and backward frame members (16) (18), which resiliently support a lower portion of a seat occupant (not shown).

As shown, a pair of known slide rail devices (22) (22) are provided via a known seat lifter mechanism (21) under the respective two side frame members (12) (12) in order to allow for not only for-and-aft adjustment, but also for height adjustment, of a seat framework (SF) or a vehicle seat. Each slide rail device (22) is basically formed by a lower rail member (22 b) adapted for fixation to a floor of vehicle (not shown) and a movable upper rail member (22 a) slidably fitted in and along the lower rail member (22 b). The seat lifter mechanism (21) includes a forward link member (21 a) and a backward link member (21 b). Since the slide rail device (22) and seat lifter mechanism (21) are not the subject matter of the present invention, any further description thereon is omitted for the sake of simplicity of description.

As is known in the art, each side frame member (12) is so formed from a rigid metallic material to have a vertical planar portion (12 a) and a peripheral flange portion (12 b). Also, as known, the peripheral flange portion (12 b) is formed integrally with all peripheral ends of the vertical planar portion (12 a) so as to project therefrom toward the outside (O) of the seat cushion frame (CF). The peripheral flange portion (12 b) per se has a function to protect a padding (not shown) and trim cover assembly (not shown) which are secured to the seat cushion frame (CF). Designation (12 b-u) and (12 b-l), respectively, denote an upper flange portion of the peripheral flange portion (12 b) and a lower flange portion of that flange portion (12 b).

Each side frame member (12) is pivotally connected via the forward and backward link members (21 a) (21 b) with each movable upper rail member (22 a).

Based on the above-described typical seat framework (SF), a description will now be made of the impact absorption structure of the present invention, with reference to FIGS. 2 to 5.

First of all, the technical concept of the present invention is based on a localized deformation of the side frame member (12) to absorb an impact transmitted from the seat back frame (BF) in the rear-end or backward collision case. In particular, an outward local deformation of the vertical planar portion (12 a) of side frame section (12), excepting the peripheral flange portion (12 b), is a best mode for achieving an effective absorption of the impact load which tends to give an excessive impact to the reclining devices (RD) or other mechanical parts provided between the seat back frame (BF) and seat cushion frame (CF), while at the same time preventing damage to a seat occupant. To realize such best mode of impact absorption, in accordance with the present invention, an importance is attached to inclination of a centroidal line extending through a vertical section of the slide frame member (12) to thereby induce a deformation at a limited local area in the vertical planar portion (12 a) of that slide frame member (12) in a direction away from a side where a seat occupant sits on the seat cushion frame (CF) or seat cushion.

Reference is now made to FIG. 2. Designation (29) denotes a reference plumb line along which, normally, the above-noted centroidal line of slide frame member (12) extends vertically or perpendicularly relative to a horizontal line (31) extending in parallel with a floor (not shown). In accordance with the present invention, the vertical section of side frame member (12) is arranged such that an upper portion of the centroidal line (or center-of-gravity line), which is designated by (28), is inclined by an angle (α) from the reference plumb line (28) in a direction to an inward side (I) facing to a side inwardly of the seat cushion frame (CF).

It is noted that the term, “inward” or “inwardly”, refers to a direction toward an inward side (I) facing to a side inwardly of the seat cushion frame (CF), whereas the term, “outward” or “outwardly”, refers to a direction toward an outward side (O) facing to a side outwardly of the seat cushion (CF).

Specifically, in the illustrated vertical section of slide frame member (12), a normal centroidal line, which corresponds to the inclined centroidal line (28), but is not inclined from the reference plumb line (29), is set by a balance in weight between the upper and lower flange portions (12-u) (12-l). In other words, according to the sectional view of FIG. 2, typically, both upper and lower flange portions (12 b-u) (12 b-l) are uniformly formed on the vertical planar portion (12 a) so as to have a same size and thus project from that vertical planar portion (12 a) outwardly in equal length. It therefore follows that the vertical planar portion (12 a) extends along the reference plumb line (29) and that an outward phantom vertical line (30), which extends along an outward vertical level toward which both upper and lower flange portions (12 b-u) (12 b-l) project horizontally, is in a substantially axisymmetric relation with an inward phantom vertical line (32) which extends along an inward vertical level toward which are oriented both inward ends (at 12 bE) of the upper and lower flange portions (12 b-u) (12 b-l).

Hence, normally, the centroidal line (at 28) accords with the reference plumb line (29) on the same line, with the vertical planar portion (12 a) of side frame member (12) extending along the reference plumb line (29), so that the outward and inward phantom vertical lines (30) (32) are in a substantially axisymmetric relation with each other with respect to the normal centroidal line. In that instance, needless to mention, the vertical section of slide frame member (12) is balanced well at both of the upper and lower portions thereof, and therefore, its centroidal line (at 28) definitely extends along the reference plumb line (29).

Now, in accordance with the present invention, generically stated, a portion of the upper flange portion (12 b-u) is extended a certain distance from the inward phantom vertical line (32) in a direction to the inward side (I), thereby inclining an upper portion of the centroidal line (28) by the angle of (α) toward that inward side (I), as shown in FIG. 2, whereby an inward weight is given to an upper portion of the slide frame member (12) at a greater ratio than to the lower portion of the same (12).

This inward inclination of centroidal line (28) is effective in reducing a strength in a local area of the lower portion of side frame member (12) (i.e. a lower area in the vertical planar portion (12 a) thereof), hence rendering that particular local area more prone to deformation than other areas of the side frame member (12) in the case where a great load or impact is transmitted from the seat back frame (BF) via the reclining device (RD) to the side frame member (12).

Further, in addition to such inclination of centroidal line (28), a module of section in the lower flange portion (12 b-l) is naturally smaller than a module of section in the upper flange portion (12 b-u), which in effect adds to reduction of the strength of the lower portion of side frame member (12) so as to facilitate the ease with which the above-elaborated local deformation occurs in the slide frame member (12).

As one example for embodying the above-described structure, as best shown in FIG. 2, there is formed an inward extension (12 c-1) in the inward end (12 bE) of the upper flange portion (12 b-u), wherein such inward end is located at the inward vertical phantom line (32) though not dearly shown, such that the upper portion of centroidal line (28) is inclined by the angle of (α) in a direction to the inward side (I). It is also appreciated that, in addition to such inclination of centroidal line (28), a module of section in the lower flange portion (12 b-l) is smaller than a module of section in the upper flange portion (12 b-u).

In this particular embodiment, referring to FIGS. 3 and 4 or 5, when a rear-end or backward collision occurs, a great load (L) is applied to the seat back frame (BF) or seat back, as described previously, with a corresponding impact being imparted via the reclining device (RD) to the side frame member (12). At this moment, as shown in FIG. 3, a certain local area of the vertical planar portion (12 a) of side frame member (12) is deformed or swollen outwardly relative to a juncture point (12 d) between the upper flange portion (12 b-u) and the vertical planar portion (12 a), thereby absorbing the impact and effectively preventing intensive creation of stress in the relatively vulnerable mechanical part of reclining device (RD) or any other mechanical part provided to the seat.

Experiments show that an optimal inclination angle (α) of the centroidal line (28) in the shown vertical section of slide frame member (12) is approximately 1.6 degrees.

With the above-described structure, the centroidal line (28) in the vertical section of side frame member (12) may be inclined in a certain area of the side frame member (12) in a direction to either the outward side (O) or the inward side (I) to thereby reduce a strength in that certain local area of side frame member (12), so that, in the case of rear-end or backward collision, the side frame member (12) is deformable at that local area thereof by an impact to be exerted thereon from the seat back frame (BF) so as to absorb the impact, thereby preventing any damage to peripheral mechanical parts including the reclining device (RD).

But, in the present embodiment, an upper portion of the centroidal line (28) is inclined by the angle (α) toward the inward side (I), which is quite advantageous in that the vertical planar portion (12 a) of side frame member (12) will be deformed to the outward side (O) away from a side where a seat occupant sits on the seat cushion frame (CF), thus insuring to avoid damage to the seat occupant.

Alternatively, instead of forming the foregoing inward extension (12 c-1), as indicated by the two-dot chain line in FIG. 2, the upper local region of the side frame member vertical planar portion (12 a) may be bent so as to be inclined inwardly, such that an upper portion of the centroidal line (28) is inclined by the angle of (α) toward the inward side (I). In this case also, as stated above, in the rear-end or backward collision case, the vertical planar portion (12 a) will be deformed to the outward side (O), thereby absorbing the impact to prevent extensive exertion of impact load on the reclining device (RD), while simultaneously avoiding damage to a seat occupant.

But, preferably, as stated earlier, the inward extension (12 c-1) be formed in the inward end (12 bE) of the upper flange portion (12 b-u), which will simplify process for forming the side frame member (12), while retaining the above-described axisymmetric relation between the upper and lower flange portions (12 b-u) (12 b-l). It is therefore possible to attain an appropriate simplified impact absorption structure of vehicle seat, without requiring any special modification or change for those two flange portions (12 b-u) (12 b-l), which means that an ordinary side frame member (12) with the typical flange portion (12 b) can be directly used, with a minimum change given thereto, in the present invention.

It is noted that the above-described kind of local deformation is limited by the forward and backward link members (21 a) (21 b) which are connected between the side frame member (12) and the slide rail member (22). Hence, the deformation is further controlled thereby so as not to reach an excessive degree that may lead to a breakage of the side frame member (12) and a serious damage to a seat occupant.

With the above-described impact absorption structure, it is to be seen that, in a rear-end or backward collision case, a great backward load (L) is applied to the seat back frame (BF) or seat back, with a corresponding amount of impact load being imparted therefrom to the side frame member (12), as a result of which, a stress is caused in a local area of the vertical planar portion (12 a) of the side frame member (12), wherein such local area is defined by a length of the foregoing inward extension (12 c-1) formed along the upper flange portion (12 b-u), and then, an outward deformation or swelling occurs in that local area, thereby absorbing the impact.

FIG. 4 shows a mode wherein the foregoing local area occupies in most area of the vertical planar portion (12 a) to provide a relatively wide deformable area (AR1), which is defined by forming a relatively long inward extension (12 c-1) in the upper flange portion (12 b-u), as indicated by the designation (L1).

In such wide deformable area (AR1), however, it is unclear where the above-stated stress caused by the great impact will be caused and a resulting deformation will be created. Thus, as shown in FIG. 5, it is preferable to set a relatively small deformable area (AR2) in the vertical planar portion (12 a) by forming the inward extension (12 c-1) in a limited or short length in and along the upper flange portion (12 b-u) as indicated by the designation (L2). This arrangement will permit the deformable area (AR2) to be minimized as desired and also defined in any desired point that will lessen a direct physical influence of the impact. For example, in the side frame member (12), the deformable area (AR2) may be set at a point which is as remotely as possible from the area where the buttock portion of seat occupant lies, with a view to minimizing a possible damage to the seat occupant, or the deformable area (AR2) be set at a point adjacent to one of the forward and backward link members (21 a) (21 b) so that a deformation degree in that area (AR2) will be minimized due to the link members (21 a or 21 b) which serves to limit the deformation of the deformable area (AR2) as stated earlier.

While having describe the present invention so far, it should be understood that the invention is not limited to the illustrated embodiments, but any modification, replacement and addition may be applied thereto without departing from scopes of the appended claims. Basically, the impact absorption structure of the present invention is applied to a front seat, but it may be applied to a rear seat. 

1. An impact absorption structure of vehicle seat, comprising; a seat cushion frame including a side frame means; the side frame means having a vertical planar portion and a peripheral flange element formed in peripheral ends of the vertical planar potion, wherein the vertical planar portion includes an upper end facing to a side upwardly of the vehicle seat and a lower end facing to a side downwardly of said vehicle seat, and said peripheral flange element includes: an upper flange portion formed in said upper end of said vertical planar portion; and a lower flange portion formed in said lower end of said vertical planar portion; and a means for making said side frame means prone to deformation by an impact imparted to said seat cushion frame, said means including a centroidal line which extends vertically along a whole vertical section of said side frame means which includes a vertical section of said upper and lower flange portions, said centroidal line having an upper portion facing to the side upwardly of said vehicle seat, wherein said means is arranged in said whole vertical section of said side frame means as well as in said vertical section of said upper and lower flange portions, such that said upper portion of said centroidal line is inclined by a predetermined angle in a direction to a side inwardly of said seat cushion frame, and that a module of section of said lower flange portion is smaller than a module of section of said upper flange portion, thereby allowing said side frame means to be deformed by said impact toward a side outwardly of said seat cushion frame, and thus absorbing the impact.
 2. The impact absorption structure of vehicle seat as claimed in claim 1, wherein said vertical planar portion of said side frame means extends along a plumb line, and wherein said means comprises an inward extension which is formed in said upper flange portion so as to extend therefrom to the side inwardly of said seat cushion frame, whereby said upper portion of said centroidal line is inclined by said predetermined angle in a direction to the side inwardly of said seat cushion frame, while said module of section of said lower flange portion is smaller than said module of section of said upper flange portion.
 3. The impact absorption structure of vehicle seat as claimed in claim 1, wherein said means is arranged in a predetermined local area of said side frame means.
 4. The impact absorption structure of vehicle seat according to claim 2, wherein said inward extension is formed in and along said upper flange portion at a limited length, so as to allow a local area of said side frame means to be deformed by said impact in a direction to the side outwardly of said seat cushion frame.
 5. The impact absorption structure of vehicle seat according to claim 4, wherein there is provided a connection means for connecting said side frame means with a seat adjustment means provided under said vehicle seat, and wherein said inward extension is disposed adjacent to said connection means, so that said local area of said side frame means is defined near to said connection means, thereby decreasing a degree of deformation of said local area. 